I made the suggestions I did, because I found out based on my experience of taking care of dogs that had anal gland issues, that the food wasn’t always the problem. Just a small piece of it.
I am hoping your veterinarian has the time to explain it in detail.
I have also learned from experience, it is best to go along with the vet’s treatment and dietary recommendations, at least until the dog is stable. Then discuss changes you would like to make (if any) with him. In other words I would be inclined to trust a vet that has examined my dog, first.
Most vets advise pet owners not to look up things on the internet, for obvious reasons.
Best of luck
